#include "stdio.h"
#include "string.h"
#include "math.h"


int main()
{

    double a,b, c,d, e,f;
    double x1,y1,x2,y2,x3,y3;
    double x,y,k[4],B[4];
    int sign[4];
	int i,j;

    while (scanf("%lf%lf%lf%lf%lf%lf",&a,&b,&c,&d,&e,&f)!=EOF)
    {

    x1=(a+c)/2;    x2=(c+e)/2;
    x3=(e+a)/2;    y1=(b+d)/2;
    y2=(d+f)/2;    y3=(f+b)/2;

    memset(sign,0,sizeof(sign));
    memset(k,0,sizeof(k));
    memset(B,0,sizeof(B));

    if (b==d) sign[1]=1;
    if (d==f) sign[2]=1;
    if (f==b) sign[3]=1;
    
    if (sign[1]==0)
    {
	k[1]=(-1)*(a-c)/(b-d);
	B[1]=y1-k[1]*x1;
    }

    if (sign[2]==0)
    {
	k[2]=(-1)*(c-e)/(d-f);
	B[2]=y2-k[2]*x2;
    }

    if (sign[3]==0)
    {
	k[3]=(-1)*(e-a)/(f-b);
	B[3]=y3-k[3]*x3;
    }


    if (sign[3]==1)
    {
	x=(B[2]-B[1])/(k[1]-k[2]);
	y=k[1]*x+B[1];
    }else if (sign[1]==1)
    {
	x=(B[3]-B[2])/(k[2]-k[3]);
	y=k[2]*x+B[2];
    }else if (sign[2]==1)
    {
	x=(B[1]-B[3])/(k[3]-k[1]);
	y=k[3]*x+B[3];
    }else
    {
       x=(B[2]-B[1])/(k[1]-k[2]);
       y=k[1]*x+B[1];     
    }


    
    k[0]=2*3.141592653589793*sqrt((a-x)*(a-x)+(b-y)*(b-y));
    printf("%.2lf\n",k[0]);
    }
    return 0;
}



